Lime mortar

A stone wall in France with lime mortar grouting being applied. Right - unapplied, Centre - lime mortar applied with a trowel, Left - lime mortar applied and then brushed with a wire brush.

Lime mortar is composed of lime and an aggregate such as sand, mixed with water. The Ancient Egyptians were the first to use lime mortars. About 6,000 years ago, they used lime to plaster the pyramids at Giza. In addition, the Egyptians also incorporated various limes into their religious temples as well as their homes. Indian traditional structures built with lime mortar, which are more than 4,000 years old like Mohenjo-daro is still a heritage monument of Indian civilization.[1] It is one of the oldest known types of mortar also used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.[2]

With the introduction of Portland cement during the 19th century, the use of lime mortar in new constructions gradually declined. This was largely due to the ease of use of Portland cement, its quick setting, and high compressive strength. However, the soft and porous properties of lime mortar provide certain advantages when working with softer building materials such as natural stone and terracotta. For this reason, while Portland cement continues to be commonly used in new constructions of brick and concrete construction, in the repair and restoration of brick and stone-built structures originally built using lime mortar, the use of Portland cement is not recommended.[3]

Despite its enduring utility over many centuries, lime mortar's effectiveness as a building material has not been well understood; time-honoured practices were based on tradition, folklore and trade knowledge, vindicated by the vast number of old buildings that remain standing. Only during the last few decades has empirical testing provided a scientific understanding of its remarkable durability.[4]

Contents

Lime comes from Old English lim "sticky substance, birdlime, mortar, cement, gluten", and is related to Latin limus "slime, mud, mire", and linere "to smear".[5]Mortar is a mixture with cement and comes from Old French mortier "builder's mortar, plaster; bowl for mixing" in the late 13th century and Latin mortarium "mortar".[5] Lime is a cement[6] which is a binder or glue which holds things together but cement is usually reserved for Portland cement.

Lime mortar today is primarily used in the conservation of buildings originally built using lime mortar, but may be used as an alternative to ordinary portland cement. It is made principally of lime (hydraulic, or non hydraulic), water and an aggregate such as sand. Portland cement has proven to be incompatible with lime mortar because it is harder, less flexible, and impermeable. These qualities lead to premature deterioration of soft, historic bricks[7] so the traditionally, low temperature fired, lime mortars are recommended for use with existing mortar of a similar type or reconstruction of buildings using historically correct methods. In the past, lime mortar tended to be mixed on site with whatever sand was locally available. Since the sand influences the colour of the lime mortar, colours of pointing mortar can vary dramatically from district to district.[8]

Hydraulic lime sets by hydration so it can set under water. Non-hydraulic lime sets by carbonatation and so needs exposure to carbon dioxide in the air and cannot set under water or inside a thick wall. For natural hydraulic lime (NHL) mortars, the lime is obtained from limestone naturally containing a sufficient percentage of silica and/or alumina. Artificial hydraulic lime is produced by introducing specific types and quantities of additives to the source of lime during the burning process, or adding a pozzolan to non-hydraulic lime. Non-hydraulic lime is produced from a high purity source of calcium carbonate such as chalk, limestone or oyster shells.

Non-hydraulic lime is primarily composed of (generally greater than 95%) calcium hydroxide, Ca(OH)2.
Non-hydraulic lime is produced by first heating sufficiently pure calcium carbonate to between 954° and 1066 °C, driving off carbon dioxide to produce quicklime (calcium oxide). This is done in a lime kiln. The quicklime is then slaked: hydrated by being thoroughly mixed with enough water to form a slurry (lime putty), or with less water to produce dry powder. This hydrated lime (calcium hydroxide) naturally turns back into calcium carbonate by reacting with carbon dioxide in the air, the entire process being called the lime cycle.

The slaking process involved in creating a lime putty is an exothermic reaction which initially creates a liquid of a creamy consistency. This is then matured for 2 to 3 months—depending upon environmental conditions—to allow time for it to condense and mature into a lime putty.

A matured lime putty is thixotropic, meaning that when a lime putty is agitated it changes from a putty into a more liquid state. This aids its use for mortars as it makes a mortar easier to work with. If left to stand following agitation a lime putty will slowly revert from a thick liquid to a putty state.[citation needed]

A frequent source of confusion regarding lime mortar stems from the similarity of the terms hydraulic and hydrated.

Hydrated lime is any lime other than quicklime, and can refer to either hydraulic (hardens under water) or non-hydraulic (does not harden under water) lime.

Lime putty is always non-hydraulic and will keep indefinitely stored under water. As the name suggests, lime putty is in the form of a putty made from just lime and water.

If the quicklime is slaked with an excess of water then putty or slurry is produced. If just the right quantity of water is used, the result is a dry material (any excess water escaping as steam during heating). This is ground to make hydrated lime powder.

Hydrated, non-hydraulic lime powder can be mixed with water to form lime putty. Before use putty is usually left in the absence of carbon dioxide (usually under water) to mature. Putty can be matured for as little as 24 hours or for many years; an increased maturation time improves the quality of the putty. There is an argument that a lime putty which has been matured for an extended period (over 12 months) becomes so stiff that it is difficult to work.

There is some dispute as to the comparative quality of putty formed from dry hydrated lime compared with that produced as putty at the time of slaking.[citation needed] It is generally agreed that the latter is preferable.[citation needed] A hydrated lime will produce a material which is not as "fatty"[clarification needed] and often, due to lengthy and poor storage, the resulting lime produced by hydrated lime will exhibit longer carbonatation periods as well as lower compressive strengths.

Non-hydraulic lime takes longer to set and is weaker than hydraulic lime, and should not be allowed to freeze before it is well set. Although the setting process can be slow, the drying time of a lime mortar must be regulated at a slow rate to ensure a good final set. A rapidly dried lime mortar will result in a low-strength, poor-quality final mortar often displaying shrinkage cracks. In practice, lime mortars are often protected from direct sunlight and wind with damp hessian sheeting or sprayed with water to control the drying rates. But it also has the quality of autogeneous healing (self healing) where some free lime dissolves in water and is redeposited in any tiny cracks which form.

Oyster Shell Mortar

The large flakes of oyster shell are a signal that this is a faux shell mortar. In fact it was a very hard Portland replacement which luckily had not done much harm to the brick.

In the tidewater region of Maryland and Virginia, oyster shells were used to produce quicklime during the colonial period. Similar to other materials used to produce lime, the oyster shells are burned. This can be done in a lime rick instead of a kiln. Burning shells in a rick is something that Colonial Williamsburg and the recreation of Ferry Farm have had to develop from conjecture and in-the-field learning. The rick that they constructed consists of logs set up in a circle that burn slowly, converting oysters that are contained in the wood pile to an ashy powder.[9][10] An explanatory video of how the rick was built for the Ferry Farm can be found here. The burnt shell can then be slaked and turned into lime putty.

Mortars using oyster shells can sometimes be identified by the presence of small bits of shell in the exposed mortar joint. In restoration masonry, the bits of shell are sometimes exaggerated to give the viewer the impression of authenticity. Unfortunately, these modern attempts often contain higher than necessary ratios of Portland cement. This can cause failures in the brick if the mortar joint is stronger than the brick elements.

When a stronger lime mortar is required, such as for external or structural purposes, a pozzolan can be added, which improves its compressive strength and helps to protect it from weathering damage. Pozzolans include powdered brick, heat treated clay, silica fume, fly ash, and volcanic materials. The chemical set imparted ranges from very weak to almost as strong as Portland cement.

This can also assist in creating more regulated setting times of the mortar as the pozzolan will create a hydraulic set, which can be of benefit in restoration projects when time scales and ultimately costs need to be monitored and maintained.

Hydraulic lime can be considered, in terms both of properties and manufacture, as part-way between non-hydraulic lime and Portland cement. The limestone used contains sufficient quantities of clay and/or silica. The resultant product will contain dicalcium silicate but unlike Portland cement not tricalcium silicate.

It is slaked enough to convert the calcium oxide to calcium hydroxide but not with sufficient water to react with the dicalcium silicate. It is this dicalcium silicate which in combination with water provides the setting properties of hydraulic lime.

Aluminium and magnesium also produce a hydraulic set, and some pozzolans contain these elements.

There are three strength grades for natural hydraulic lime, laid down in the European Norm EN459; NHL2, NHL3.5 and NHL5. The numbers stand for the minimum compressive strength at 28 days in newtons per square millimeter (N/mm2). For example, the NHL 3.5 strength ranges from 3.5 N/mm2 (510 psi) to 10 N/mm2 (1,450 psi).[11] These are similar to the old classification of feebly hydraulic, moderately hydraulic and eminently hydraulic, and although different, some people continue to refer to them interchangeably. The terminology for hydraulic lime mortars was improved by the skilled French civil engineer Louis Vicat in the 1830s from the older system of water limes and feebly, moderately and eminently. Vicat published his work following research of the use of lime mortars whilst building bridges and roads in his work. The French company Vicat still currently produce natural cements and lime mortars.[12] Names of lime mortars were so varied and conflicting across the European continent that the reclassification has greatly improved the understanding and use of lime mortars.

Traditional lime mortar is a combination of lime putty and aggregate (usually sand). A typical modern lime mortar mix would be 1 part lime putty to 3 parts washed, well graded, sharp sand. Other materials have been used as aggregate instead of sand. The theory is that the voids of empty space between the sand particles account for a 1/3 of the volume of the sand. The lime putty when mixed at a 1 to 3 ratio, fill these voids to create a compact mortar. Analysis of mortar samples from historic buildings typically indicates a higher ratio of around 1 part lime to 2 part aggregate/sand was commonly used. A traditional coarse plaster mix also had horse hair added for reinforcing and control of shrinkage, important when plastering to wooden laths and for base (or dubbing) coats onto uneven surfaces such as stone walls where the mortar is often applied in thicker coats to compensate for the irregular surface levels.

If shrinkage and cracking of the lime mortar does occur this can be as a result of either

The sand being poorly graded or with a particle size that is too small

The mortar being applied too thickly (Thicker coats increase the possibility of shrinkage, cracking and slumping)

Too much suction from the substrate

High air temperatures or direct sunlight which force dry the mortar

High water content in the lime mortar mix

Poor quality or unmatured lime putty

A common method for mixing lime mortar with powdered lime is as follows:

Gather your ingredients, sand, lime, and water

Measure out your ratio of sand to lime, for example 3 buckets of sand, and 1 bucket of lime for a 3:1 ratio.

Mix the dry ingredients thoroughly so all the sand is coated with lime, and there are neither chunks of sand or lime visible.

Reserve some portion of the dry ingredients by removing it from your mixing vessel. The amount reserved can vary, but a safe starting point is about 1/4 of the batch. This will be added in later to fine tune the dryness of the mix.

Measure out water. How much depends on how wet you want your mix to be, and how damp/wet your sand is. A good starting point is 1 quart of water per gallon of sand.

Add about 2/3 of the water to your dry ingredients and mix until even consistency.

Add the reserved dry ingredients and/or the remaining water to get a mix you like. It takes time to know what works well, and the recipe can change depending on the temperature, humidity, moisture in the sand, type of brick, and task at hand (laying brick may warrant a wetter mix, while pointing may require a drier one.

To test the mix as you are making it, you can use a trowel, or pat the mortar with your hand to see how much moisture and "cream" come to the surface.

Remember to thoroughly wet your brick prior to using lime mortar. Old brick can be extremely porous, a 4lb brick can hold a pint of water. The bricks should be saturated, but dry on the surface prior to laying or pointing. Excess water can cause the lime to run and leave streaks.

Hair reinforcement is not found in lime mortars, but is common in lime plaster and many types of hair and other organic fibres can be found in historic plasters.[13] However, organic material in lime will degrade in damp environments particularly on damp external renders.[14] This problem has given rise to the use of polypropylene fibres in new lime renders[13]

Lime mortar is not as strong in compression as Portland cement based mortar, but both are sufficiently strong for construction of non-high-rise domestic properties.

Lime mortar does not adhere as strongly to masonry as Portland cement. This is an advantage with softer types of masonry, where use of cement in many cases eventually results in cement pulling away some masonry material when it reaches the end of its life. The mortar is a sacrificial element which should be weaker than the bricks so it will crack before the bricks. It is less expensive to replace cracked mortar than cracked bricks.

Under cracking conditions, Portland cement breaks, whereas lime often produces numerous microcracks if the amount of movement is small. These microcracks recrystallise through the action of 'free lime' effectively self-healing the affected area.

Historic buildings are frequently constructed with relatively soft masonry units (e.g. soft brick and many types of stone), and minor movement in such buildings is quite common due to the nature of the foundations. This movement breaks the weakest part of the wall, and with Portland cement mortar this is usually the masonry. When lime mortar is used, the lime is the weaker element, and the mortar cracks in preference to the masonry. This results in much less damage, and is relatively simple to repair.

Lime mortar is more porous than cement mortars, and it wicks any dampness in the wall to the surface where it evaporates. Thus any salt content in the water crystallises on the lime, damaging the lime and thus saving the masonry. Cement on the other hand evaporates water less than soft brick, so damp issues are liable to cause salt formation and spalling on brick surfaces and consequent disintegration of bricks.[15][16] This damp evaporation ability is widely referred to as 'breathability'.

Lime mortar should not be used below temperatures of 5 °C (41 °F) and takes longer to set so it should be protected from freezing for three months. Because of it's faster set, hydraulic lime may not need as much time before freezing temperatures begin.

Usually any dampness in the wall will cause the lime mortar to change colour, indicating the presence of moisture. The effect will create an often mottled appearance of a limewashed wall. As the moisture levels within a wall alter, so will the shade of a limewash. The darker the shade of limewash, the more pronounced this effect will become.

A load of mixed lime mortar may be allowed to sit as a lump for some time, without it drying out (it may get a thin crust). When ready to use, this lump may be remixed ('knocked up') again and then used. Traditionally on building sites, prior to the use of mechanical mixers, the lime putty (slaked on site in a pit) was mixed with sand by a labourer who would "beat and ram" the mix with a "larry" (a wide hoe with large holes). This was then covered with sand and allowed to sit for a while (from days to weeks) - a process known as 'banking'. This lump was then remixed and used as necessary. This process cannot be done with Portland cement.

The combination of Portland cement and lime is used for stabilization and solidification of the ground through establishing of lime cement columns or stabilization of the entire upper mass volume.[17] The method provides an increase in strength when it comes to vibrations, stability and settling. When building e.g. roads and railways, the method is more common and widespread (Queen Eufemias street in Central Oslo, E18 at Tønsberg etc.).[citation needed]

For preservation purposes, Type N and Type O mortars are often used. A Type N mortar is 1 part Portland, 1 part Lime and 6 parts sand or other aggregate (1:1:6). A Type O mortar is 1 part Portland, 2 parts Lime and 9 parts sand or other aggregate (1:2:9). The Type L mortar has no Portland, and 1 part Lime to 3 parts sand or other aggregate. The addition of cement or other pozzolan to decrease cure times is referred to as “gauging.” Other than Portland, ash and brick dust have been used to gauge mortars.[18]

Spalling of brick in an 18th century chimney. The lower section is older than the upper. Note that the while the lower mortar is deteriorated, it is not as bad as the brick.

For historic restoration purposes, and restoration work involving repointing or brick replacement, masons must discover the original brick and mortar and repair it with a similar material. The National Park Service provides guidance for proper masonry repointing through Preservation Brief 2.[19] In general, Brief 2 suggests that repointing should be done with a similar or weaker mortar. Therefore, a straight lime mortar joint should be repointed in kind. Due to the popularity of Portland cement, this often is not the case. A wall system needs a balance between the mortar and brick that allows the mortar to be the weak part of the unit. When mortar is stronger than the brick, it prevents any natural movement in the wall and the faces of the brick will begin to deteriorate, a process known as spalling, the process by which the outer face of a brick degrades and can flake off or turn to powder. There is also a natural movement of water through a masonry wall. A strong Portland cement mix will prevent a free flow of water from a moist to dry area. This can cause rising damp to be trapped within the wall and create system failures. If moisture can not escape into the air, it will cause damage to a wall structure. Water freezing in the wall is another cause of spalling.

In restoration work of pre-20th century structures, there should be a high ratio of lime and aggregate to Portland. This reduces the compressive strength of the mortar but allows the wall system to function better. The lime mortar acts as a wick that helps to pull water from the brick. This can help to prevent the older brick from spalling. Even when the brick is a modern, harder element, repointing with a higher ratio lime mortar may help to reduce rising damp.

It may not be advisable for all consumers to use a type L mortar. With no Portland in the mix, there is less control over the setting of the mortar. In some cases, a freeze thaw cycle will be enough to create failure in the mortar joint. Type L mortar can also take a long time to fully cure and therefore work needs to be performed at a time of year where the weather conditions are conducive to the mortar setting properly. Those conditions are not only above freezing temperatures but also drier seasons. To protect the slow curing mortar from damp, a siloxane can be added to the surface. With historic structures, this may be a controversial strategy as it could have a detrimental effect to the historic fabric.

The presence of Portland allows for a more stable mortar. The stability and predictability make the mixed mortar more user friendly, particularly in applications where entire wall sections are being laid. Contractors and designers may prefer mixes that contain Portland due to the increased compressive strength over a straight lime mortar. As many pre-Portland mix buildings are still standing and have original mortar, the arguments for greater compressive strength and ease of use may be more a result of current practice and a lack of understanding of older techniques.

1.
Mortar (masonry)
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In its broadest sense mortar includes pitch, asphalt, and soft mud or clay, such as used between mud bricks. Mortar comes from Latin mortarium meaning crushed, mortars are typically made from a mixture of sand, a binder, and water. The most common binder since the early 20th century is Portland cement, there are several types of cement mortars and additives. The first mortars were made of mud and clay, because of a lack of stone and an abundance of clay, Babylonian constructions were of baked brick, using lime or pitch for mortar. According to Roman Ghirshman, the first evidence of using a form of mortar was at the Mehrgarh of Baluchistan in Pakistan. The ancient sites of Harappan civilization of third millennium BCE are built with kiln-fired bricks, gypsum mortar, also called plaster of Paris, was used in the construction of the Egyptian pyramids and many other ancient structures. It is made from gypsum, which requires a firing temperature. It is therefore easier to make lime mortar and sets up much faster which may be a reason it was used as the typical mortar in ancient, brick arch. Gypsum mortar is not as durable as other mortars in damp conditions, in early Egyptian pyramids, which were constructed during the Old Kingdom, the limestone blocks were bound by mortar of mud and clay, or clay and sand. In later Egyptian pyramids, the mortar was made of gypsum or lime. Gypsum mortar was essentially a mixture of plaster and sand and was quite soft, in the Indian subcontinent, multiple cement types have been observed in the sites of the Indus Valley Civilization, such as the Mohenjo-daro city-settlement that dates to earlier than 2600 BCE. Bitumen mortar was used at a lower-frequency, including in the Great Bath at Mohenjo-daro. Historically, building with concrete and mortar next appeared in Greece, the excavation of the underground aqueduct of Megara revealed that a reservoir was coated with a pozzolanic mortar 12 mm thick. This aqueduct dates back to c.500 BCE, pozzolanic mortar is a lime based mortar, but is made with an additive of volcanic ash that allows it to be hardened underwater, thus it is known as hydraulic cement. The Greeks obtained the volcanic ash from the Greek islands Thira and Nisiros, or from the then Greek colony of Dicaearchia near Naples, the Romans later improved the use and methods of making what became known as pozzolanic mortar and cement. Even later, the Romans used a mortar without pozzolana using crushed terra cotta, introducing aluminum oxide and this mortar was not as strong as pozzolanic mortar, but, because it was denser, it better resisted penetration by water. Hydraulic mortar was not available in ancient China, possibly due to a lack of volcanic ash, around 500 CE, sticky rice soup was mixed with slaked lime to make an inorganic−organic composite mortar that had more strength and water resistance than lime mortar. It is not understood how the art of making hydraulic mortar and cement, during the Middle Ages when the Gothic cathedrals were being built, the only active ingredient in the mortar was lime

2.
Construction aggregate
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Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete, aggregates are also used as base material under foundations, roads, and railroads. Preferred bitumenous aggregate sizes for road construction are given in EN13043 as d/D, the same classification sizing is used for larger armour stone sizes in EN13383, EN12620 for concrete aggregate, EN13242 for base layers of road construction and EN13450 for railway ballast. These products include specific types of coarse and fine aggregate designed for such uses as additives to asphalt and concrete mixes, state transportation departments further refine aggregate material specifications in order to tailor aggregate use to the needs and available supply in their particular locations. In addition, there are materials that are used as specialty lightweight aggregates, clay, pumice, perlite. People have used sand and stone for foundations for thousands of years, significant refinement of the production and use of aggregate occurred during the Roman Empire, which used aggregate to build its vast network of roads and aqueducts. The invention of concrete, which was essential to architecture utilizing arches, created an immediate, vitruvius writes in De architectura, Economy denotes the proper management of materials and of site, as well as a thrifty balancing of cost and common sense in the construction of works. This will be observed if, in the first place, the architect does not demand things which cannot be found or made ready without great expense, for example, it is not everywhere that there is plenty of pit-sand, rubble, fir, clear fir, and marble. Where there is no pit sand, we must use the kinds washed up by rivers or by the sea. the advent of modern blasting methods enabled the development of quarries, which are now used throughout the world, wherever competent bedrock deposits of aggregate quality exist. In many places, good limestone, granite, marble or other quality stone bedrock deposits do not exist, in these areas, natural sand and gravel are mined for use as aggregate. Where neither stone, nor sand and gravel, are available, construction demand is satisfied by shipping in aggregate by rail. Additionally, demand for aggregates can be satisfied through the use of slag. However, the available tonnages and lesser quality of these materials prevent them from being a replacement for mined aggregates on a large scale. Large stone quarry and sand and gravel operations exist near virtually all population centers, limestone and granite are also produced in large amounts as dimension stone. The great majority of crushed stone is moved by truck from the quarry/plant to the first point of sale or use. According to the USGS,2006 U. S. sand and gravel production was 1.32 billion tonnes valued at $8.54 billion, the great majority of this was again moved by truck, instead of by electric train. Currently, total U. S. aggregate demand by final market sector was 30%–35% for non-residential building, 25% for highways, the largest-volume of recycled material used as construction aggregate is blast furnace and steel furnace slag. Blast furnace slag is either air-cooled or granulated, if the granulated blast furnace slag accesses free lime during hydration, it develops strong hydraulic cementitious properties and can partly substitute for portland cement in concrete

3.
Sand
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Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt, Sand can also refer to a textural class of soil or soil type, i. e. a soil containing more than 85% sand-sized particles by mass. The second most common type of sand is calcium carbonate, for example aragonite, for example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non renewable resource over human timescales, and sand suitable for making concrete is in high demand, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this size is termed a sand grain. Sand grains are between gravel and silt, a 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers. ISO14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size, very fine sand, fine sand, medium sand, coarse sand, and very coarse sand. These sizes are based on the Krumbein phi scale, where size in Φ = -log2D, on this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers. The composition of sand is highly variable, depending on the local rock sources. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum, Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic with a high olivine content, many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, the study of individual grains can reveal much historical information as to the origin and kind of transport of the grain. Quartz sand that is weathered from granite or gneiss quartz crystals will be angular. It is called grus in geology or sharp sand in the trade where it is preferred for concrete. Sand that is transported long distances by water or wind will be rounded, people who collect sand as a hobby are known as arenophiles

4.
Ancient Egypt
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Ancient Egypt was a civilization of ancient Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. It is one of six civilizations to arise independently, Egyptian civilization followed prehistoric Egypt and coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh Narmer. In the aftermath of Alexander the Greats death, one of his generals, Ptolemy Soter and this Greek Ptolemaic Kingdom ruled Egypt until 30 BC, when, under Cleopatra, it fell to the Roman Empire and became a Roman province. The success of ancient Egyptian civilization came partly from its ability to adapt to the conditions of the Nile River valley for agriculture, the predictable flooding and controlled irrigation of the fertile valley produced surplus crops, which supported a more dense population, and social development and culture. Its art and architecture were widely copied, and its antiquities carried off to far corners of the world and its monumental ruins have inspired the imaginations of travelers and writers for centuries. The Nile has been the lifeline of its region for much of human history, nomadic modern human hunter-gatherers began living in the Nile valley through the end of the Middle Pleistocene some 120,000 years ago. By the late Paleolithic period, the climate of Northern Africa became increasingly hot and dry. In Predynastic and Early Dynastic times, the Egyptian climate was less arid than it is today. Large regions of Egypt were covered in treed savanna and traversed by herds of grazing ungulates, foliage and fauna were far more prolific in all environs and the Nile region supported large populations of waterfowl. Hunting would have been common for Egyptians, and this is also the period when many animals were first domesticated. The largest of these cultures in upper Egypt was the Badari, which probably originated in the Western Desert, it was known for its high quality ceramics, stone tools. The Badari was followed by the Amratian and Gerzeh cultures, which brought a number of technological improvements, as early as the Naqada I Period, predynastic Egyptians imported obsidian from Ethiopia, used to shape blades and other objects from flakes. In Naqada II times, early evidence exists of contact with the Near East, particularly Canaan, establishing a power center at Hierakonpolis, and later at Abydos, Naqada III leaders expanded their control of Egypt northwards along the Nile. They also traded with Nubia to the south, the oases of the desert to the west. Royal Nubian burials at Qustul produced artifacts bearing the oldest-known examples of Egyptian dynastic symbols, such as the crown of Egypt. They also developed a ceramic glaze known as faience, which was used well into the Roman Period to decorate cups, amulets, and figurines. During the last predynastic phase, the Naqada culture began using written symbols that eventually were developed into a system of hieroglyphs for writing the ancient Egyptian language. The Early Dynastic Period was approximately contemporary to the early Sumerian-Akkadian civilisation of Mesopotamia, the third-century BC Egyptian priest Manetho grouped the long line of pharaohs from Menes to his own time into 30 dynasties, a system still used today

5.
Pyramid
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A pyramid is a structure whose outer surfaces are triangular and converge to a single point at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, as such, a pyramid has at least three outer triangular surfaces. The square pyramid, with base and four triangular outer surfaces, is a common version. A pyramids design, with the majority of the closer to the ground. This distribution of weight allowed early civilizations to create stable monumental structures and it has been demonstrated that the common shape of the pyramids of antiquity, from Egypt to Central America, represents the dry-stone construction that requires minimum human work. Pyramids have been built by civilizations in many parts of the world, khufus Pyramid is built mainly of limestone, and is considered an architectural masterpiece. It contains over 2,000,000 blocks ranging in weight from 2.5 tonnes to 15 tonnes and is built on a base with sides measuring about 230 m. Its four sides face the four cardinal points precisely and it has an angle of 52 degrees and it is still the tallest pyramid. The largest pyramid by volume is the Great Pyramid of Cholula, the Mesopotamians built the earliest pyramidal structures, called ziggurats. In ancient times, these were painted in gold/bronze. Since they were constructed of sun-dried mud-brick, little remains of them, ziggurats were built by the Sumerians, Babylonians, Elamites, Akkadians, and Assyrians for local religions. Each ziggurat was part of a complex which included other buildings. The precursors of the ziggurat were raised platforms that date from the Ubaid period during the fourth millennium BC, the earliest ziggurats began near the end of the Early Dynastic Period. The latest Mesopotamian ziggurats date from the 6th century BC, built in receding tiers upon a rectangular, oval, or square platform, the ziggurat was a pyramidal structure with a flat top. Sun-baked bricks made up the core of the ziggurat with facings of fired bricks on the outside, the facings were often glazed in different colors and may have had astrological significance. Kings sometimes had their names engraved on these glazed bricks, the number of tiers ranged from two to seven. It is assumed that they had shrines at the top, but there is no evidence for this. Access to the shrine would have been by a series of ramps on one side of the ziggurat or by a ramp from base to summit

6.
Mohenjo-daro
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Mohenjo-daro is an archeological site in the province of Sindh, Pakistan. Mohenjo-daro was abandoned in the 19th century BCE as the Indus Valley Civilization declined, significant excavation has since been conducted at the site of the city, which was designated an UNESCO World Heritage Site in 1980. The site is threatened by erosion and improper restoration. Mohenjo-daro, the name for the site, has been variously interpreted as Mound of the Dead Men in Sindhi. The citys original name is unknown, based on his analysis of a Mohenjo-daro seal, Iravatham Mahadevan speculates that the citys ancient name could have been Kukkutarma. Cock-fighting may have had ritual and religious significance for the city, with domesticated chickens bred there for sacred purposes, Mohenjo-daro may also have been a point of diffusion for the eventual worldwide domestication of chickens. Mohenjo-daro is located west of the Indus River in Larkana District, Sindh, Pakistan and it is sited on a Pleistocene ridge in the middle of the flood plain of the Indus River Valley, around 28 kilometres from the town of Larkana. The Indus still flows east of the site, but the Ghaggar-Hakra riverbed on the side is now dry. Mohenjo-daro was built in the 26th century BCE and it was one of the largest cities of the ancient Indus Valley Civilization, also known as the Harappan Civilization, which developed around 3,000 BCE from the prehistoric Indus culture. Mohenjo-daro was the most advanced city of its time, with remarkably sophisticated civil engineering, when the Indus civilization went into sudden decline around 1900 BCE, Mohenjo-daro was abandoned. The ruins of the city remained undocumented for around 3,700 years until R. D and this led to large-scale excavations of Mohenjo-daro led by Kashinath Narayan Dikshit in 1924–25, and John Marshall in 1925–26. In the 1930s, major excavations were conducted at the site under the leadership of Marshall, D. K. Dikshitar, further excavations were carried out in 1945 by Ahmad Hasan Dani and Mortimer Wheeler. The last major series of excavations were conducted in 1964 and 1965 by Dr. George F. Dales, a dry core drilling conducted in 2015 by Pakistans National Fund for Mohenjo-daro revealed that the site is larger than the unearthed area. Mohenjo-daro has a layout based on a street grid of rectilinear buildings. Most were built of fired and mortared brick, some incorporated sun-dried mud-brick, the covered area of Mohenjo-daro is estimated at 300 hectares. The Oxford Handbook of Cities in World History offers an estimate of a peak population of around 40,000. The sheer size of the city, and its provision of buildings and facilities. The city is divided into two parts, the so-called Citadel and the Lower City

7.
Ancient Rome
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In its many centuries of existence, the Roman state evolved from a monarchy to a classical republic and then to an increasingly autocratic empire. Through conquest and assimilation, it came to dominate the Mediterranean region and then Western Europe, Asia Minor, North Africa and it is often grouped into classical antiquity together with ancient Greece, and their similar cultures and societies are known as the Greco-Roman world. Ancient Roman civilisation has contributed to modern government, law, politics, engineering, art, literature, architecture, technology, warfare, religion, language and society. Rome professionalised and expanded its military and created a system of government called res publica, the inspiration for modern republics such as the United States and France. By the end of the Republic, Rome had conquered the lands around the Mediterranean and beyond, its domain extended from the Atlantic to Arabia, the Roman Empire emerged with the end of the Republic and the dictatorship of Augustus Caesar. 721 years of Roman-Persian Wars started in 92 BC with their first war against Parthia and it would become the longest conflict in human history, and have major lasting effects and consequences for both empires. Under Trajan, the Empire reached its territorial peak, Republican mores and traditions started to decline during the imperial period, with civil wars becoming a prelude common to the rise of a new emperor. Splinter states, such as the Palmyrene Empire, would divide the Empire during the crisis of the 3rd century. Plagued by internal instability and attacked by various migrating peoples, the part of the empire broke up into independent kingdoms in the 5th century. This splintering is a landmark historians use to divide the ancient period of history from the pre-medieval Dark Ages of Europe. King Numitor was deposed from his throne by his brother, Amulius, while Numitors daughter, Rhea Silvia, because Rhea Silvia was raped and impregnated by Mars, the Roman god of war, the twins were considered half-divine. The new king, Amulius, feared Romulus and Remus would take back the throne, a she-wolf saved and raised them, and when they were old enough, they returned the throne of Alba Longa to Numitor. Romulus became the source of the citys name, in order to attract people to the city, Rome became a sanctuary for the indigent, exiled, and unwanted. This caused a problem for Rome, which had a large workforce but was bereft of women, Romulus traveled to the neighboring towns and tribes and attempted to secure marriage rights, but as Rome was so full of undesirables they all refused. Legend says that the Latins invited the Sabines to a festival and stole their unmarried maidens, leading to the integration of the Latins, after a long time in rough seas, they landed at the banks of the Tiber River. Not long after they landed, the men wanted to take to the sea again, one woman, named Roma, suggested that the women burn the ships out at sea to prevent them from leaving. At first, the men were angry with Roma, but they realized that they were in the ideal place to settle. They named the settlement after the woman who torched their ships, the Roman poet Virgil recounted this legend in his classical epic poem the Aeneid

8.
Ancient Greece
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Ancient Greece was a civilization belonging to a period of Greek history from the Greek Dark Ages of the 12th-9th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and this was followed by the period of Classical Greece, an era that began with the Greco-Persian Wars, lasting from the 5th to 4th centuries BC. Due to the conquests by Alexander the Great of Macedonia, Hellenistic civilization flourished from Central Asia to the end of the Mediterranean Sea. Classical Greek culture, especially philosophy, had a influence on ancient Rome. For this reason Classical Greece is generally considered to be the culture which provided the foundation of modern Western culture and is considered the cradle of Western civilization. Classical Antiquity in the Mediterranean region is considered to have begun in the 8th century BC. Classical Antiquity in Greece is preceded by the Greek Dark Ages and this period is succeeded, around the 8th century BC, by the Orientalizing Period during which a strong influence of Syro-Hittite, Jewish, Assyrian, Phoenician and Egyptian cultures becomes apparent. The end of the Dark Ages is also dated to 776 BC. The Archaic period gives way to the Classical period around 500 BC, Ancient Periods Astronomical year numbering Dates are approximate, consult particular article for details The history of Greece during Classical Antiquity may be subdivided into five major periods. The earliest of these is the Archaic period, in which artists made larger free-standing sculptures in stiff, the Archaic period is often taken to end with the overthrow of the last tyrant of Athens and the start of Athenian Democracy in 508 BC. It was followed by the Classical period, characterized by a style which was considered by observers to be exemplary, i. e. classical, as shown in the Parthenon. This period saw the Greco-Persian Wars and the Rise of Macedon, following the Classical period was the Hellenistic period, during which Greek culture and power expanded into the Near and Middle East. This period begins with the death of Alexander and ends with the Roman conquest, Herodotus is widely known as the father of history, his Histories are eponymous of the entire field. Herodotus was succeeded by authors such as Thucydides, Xenophon, Demosthenes, Plato, most of these authors were either Athenian or pro-Athenian, which is why far more is known about the history and politics of Athens than those of many other cities. Their scope is limited by a focus on political, military and diplomatic history, ignoring economic. In the 8th century BC, Greece began to emerge from the Dark Ages which followed the fall of the Mycenaean civilization, literacy had been lost and Mycenaean script forgotten, but the Greeks adopted the Phoenician alphabet, modifying it to create the Greek alphabet. The Lelantine War is the earliest documented war of the ancient Greek period and it was fought between the important poleis of Chalcis and Eretria over the fertile Lelantine plain of Euboea. Both cities seem to have suffered a decline as result of the long war, a mercantile class arose in the first half of the 7th century BC, shown by the introduction of coinage in about 680 BC

9.
Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes

10.
Gypsum
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Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely mined and is used as a fertilizer, and as the constituent in many forms of plaster, blackboard chalk. Mohs scale of hardness, based on scratch Hardness comparison. It forms as a mineral and as a hydration product of anhydrite. The word gypsum is derived from the Greek word γύψος, plaster, because the quarries of the Montmartre district of Paris have long furnished burnt gypsum used for various purposes, this dehydrated gypsum became known as plaster of Paris. Upon addition of water, after a few tens of minutes plaster of Paris becomes regular gypsum again, causing the material to harden or set in ways that are useful for casting, Gypsum was known in Old English as spærstān, spear stone, referring to its crystalline projections. Gypsum may act as a source of sulfur for plant growth, which was discovered by J. M. Mayer, american farmers were so anxious to acquire it that a lively smuggling trade with Nova Scotia evolved, resulting in the so-called Plaster War of 1820. In the 19th century, it was known as lime sulfate or sulfate of lime. Gypsum is moderately water-soluble and, in contrast to most other salts, it exhibits retrograde solubility, when gypsum is heated in air it loses water and converts first to calcium sulfate hemihydrate, and, if heated further, to anhydrous calcium sulfate. As for anhydrite, its solubility in saline solutions and in brines is also dependent on NaCl concentration. Gypsum crystals are found to contain water and hydrogen bonding. Gypsum occurs in nature as flattened and often twinned crystals, and transparent, selenite contains no significant selenium, rather, both substances were named for the ancient Greek word for the Moon. Selenite may also occur in a silky, fibrous form, in case it is commonly called satin spar. Finally, it may also be granular or quite compact, in hand-sized samples, it can be anywhere from transparent to opaque. A very fine-grained white or lightly tinted variety of gypsum, called alabaster, is prized for ornamental work of various sorts, in arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose. It also forms some of the largest crystals found in nature, up to 12 m long, Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon, Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures and it is often associated with the minerals halite and sulfur

11.
Portland cement
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Portland cement is the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco, and most non-speciality grout. It was developed from other types of lime in England in the mid 19th century. It is a fine powder produced by heating materials in a kiln to form what is called clinker, grinding the clinker, and adding small amounts of other materials. Several types of Portland cement are available, with the most common being called ordinary Portland cement which is grey in color, Portland cement is caustic, so it can cause chemical burns. The powder can cause irritation or, with exposure, lung cancer and can contain some hazardous components such as crystalline silica. Concrete produced from Portland cement is one of the most versatile construction materials available in the world, Portland cement was developed from natural cements made in Britain beginning in the middle of the 18th century. Its name is derived from its similarity to Portland stone, a type of building stone quarried on the Isle of Portland in Dorset, England. In the late 18th century, Roman cement was developed and patented in 1796 by James Parker, Roman cement quickly became popular, in 1811 James Frost produced a cement he called British cement. James Frost is reported to have erected a manufactory for making of an artificial cement in 1826, in 1843, Aspdins son William improved their cement, which was initially called Patent Portland cement, although he had no patent. In 1818, French engineer Louis Vicat invented a hydraulic lime considered the principal forerunner of Portland cement. Edgar Dobbs of Southwark patented a cement of this kind in 1811, Portland cement was used by Joseph Aspdin in his cement patent in 1824 because of the cements resemblance to Portland stone. The name Portland cement is also recorded in a directory published in 1823 being associated with a William Lockwood, a Dave Stewart, however, Aspdins cement was nothing like modern Portland cement but was a first step in the development of modern Portland cement, called a proto-Portland cement. William Aspdin had left his fathers company and in his cement manufacturing apparently accidentally produced calcium silicates in the 1840s, in 1848, William Aspdin further improved his cement, in 1853, he moved to Germany, where he was involved in cement making. William Aspdin made what could be called meso-Portland cement, isaac Charles Johnson further refined the production of meso-Portland cement and claimed to be the real father of Portland cement. John Grant of the Metropolitan Board of Works in 1859 set out requirements for cement to be used in the London sewer project and this became a specification for Portland cement. The Hoffman endless kiln which gave control over combustion was tested in 1860. This cement was made at the Portland Cementfabrik Stern at Stettin and it is thought that the first modern Portland cement was made there. The Association of German Cement Manufacturers issued a standard on Portland cement in 1878, by the early 20th century American-made Portland cement had displaced most of the imported Portland cement

12.
Terracotta
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Terracotta, terra cotta or terra-cotta, a type of earthenware, is a clay-based unglazed or glazed ceramic, where the fired body is porous. The term is used to refer to the natural, brownish orange color, of most terracotta. This article covers the senses of terracotta as a medium in sculpture, as in the Terracotta Army and Greek terracotta figurines, asian and European sculpture in porcelain is not covered. Glazed architectural terracotta and its version as exterior surfaces for buildings were used in Asia for some centuries before becoming popular in the West in the 19th century. In archaeology and art history, terracotta is used to describe objects such as figurines not made on a potters wheel. An appropriate refined clay is formed to the desired shape, after drying it is placed in a kiln or atop combustible material in a pit, and then fired. The typical firing temperature is around 1,000 °C, though it may be as low as 600 °C in historic and archaeological examples. In some contexts, such as Roman figurines, white-colored terracotta is known as pipeclay, as such clays were later preferred for tobacco pipes, fired terracotta is not watertight, but surface-burnishing the body before firing can decrease its porousness and a layer of glaze can make it watertight. It is suitable for use below ground to carry pressurized water, for garden pots or building decoration in many environments, most other uses, such as for tableware, sanitary piping, or building decoration in freezing environments, require the material to be glazed. Terracotta, if uncracked, will ring if lightly struck, painted terracotta is typically first covered with a thin coat of gesso, then painted. It has been widely used but the paint is only suitable for indoor positions and is much less durable than fired colors in or under a ceramic glaze. Terracotta sculpture was rarely left in its raw fired state in the West until the 18th century. Terracotta/earthenware was the known type of ceramic produced by Western and pre-Columbian people until the 14th century. Terracotta has been used throughout history for sculpture and pottery as well as for bricks, in ancient times, the first clay sculptures were dried in the sun after being formed. They were later placed in the ashes of open hearths to harden, however, only after firing to high temperature would it be classed as a ceramic material. Terracotta female figurines were uncovered by archaeologists in excavations of Mohenjo-daro, along with phallus-shaped stones, these suggest some sort of fertility cult and a belief in a mother goddess. The Burney Relief is a terracotta plaque from Ancient Mesopotamia of about 1950 BC. In Mesoamerica, the majority of Olmec figurines were in terracotta